Method of manufacturing lenses and apparatus therefor



Sept. 8, 1931. F. 1. G. B. WATSON ET AL 1,822,606

METHOD OF MANUFACTURING LENSES AND APPARATUS THEREFOR Filed NOV. 24, 1928 fkANC/ JHH (y'EarfqE f'ucf marsan, EDWARD CULVER, ALFRED HENRY EMERSON,

album l sinks, so that parts used for this purpose will Patented Sept. 8, 1931 UNITED STATE-s PA'riazN'rcritter;

FRANCIS JOHN GEORGE BRUCE WATSON, OF ISLINGTON, LONDON, EDWARD CULVER, OF CROUCH END, LONDON, AND ALFRED HENRY`EMERSON, OF FINCHLEY, LONDON, vENGLAIFD, `ASSIGrNORS T0 'UNITED KINGDOM OPTICAL COMP/ANY, LIMITED, OF

LONDON', ENGLAND METHOD OF MANUFACTURING LENSES AND APPARATUS THEREFOR Applica/cin mea Nvember 24, 192s. serial No. 321,602.

Our invention relates to an apparatus and method of manufacturing lenses.

In particular it is our object to provide a method of manufacturing bifoca'l lenses with a minimum of loss, by reason of the presence of air bubbles, reflecting surfaces, warping and the like.

It is a further object to provide a method Aand means of fusing parts of the button t0- gether and of fusing the buttons to counternot bring about warping, twisting or displacement of the parts one to the other, so that the feelers and the means used for main taining the feelers in position will disappear and whatever parts are remaining can be eliminated in the finished product by grindlrlhe invention with its various novel fea-4 tures is illustrated in the accon'ipanying drawings with reference to which it will now be described.

Referring to the drawings,

Figure 1 is a plan view of a plurality of unfused buttons ready for introduction into the furnace to be fused,

Figure 2 is a section on the line 2-2 of Figure 1 looking in the direction of the arrows,

Figure 3 is a top plan view of a countersink with an unfused button in position,

Figure 4 is a section (enlarged) on the line 4 4 of Figure 3,

Figure 5 is a side elevation of one of the crown strips or sections of the button showing its grey edge,

Figure 6 is a top plan view of the fused Y countersink and button after grinding,

Figure 7 is a detail perspective of the small feeler enlarged,

Figure 8 is a section through the countersink in its final fused condition on the line 4-4 after fusing and grinding,

Figure 9 is an enlarged deta'il section showing'the application of adhesive and feelers to the button and countersink.

Referring to the drawings in detail, 1 is the bottom of a trough-like tray having side walls 2. This tray is of metal. On the bottom of the tray is located a strip of asbestos 3. Between the side walls of the tray and upon this asbestos strip 3 we locate groups of flint and crown glass pieces or strips which when fused and trimmed round constitute a button. These groups can be in single or double rows with spring pressure in centre or on one side. The crown strips are designated 4 and the flint intermediate strip is designated 5. v

This strip 5 later becomes the fused zonal insert that appears in the final lens as a part appreciable period of time of approximately 15 minutes at approximately 650 C. temperature. .":Upon being withdrawn the fused square buttons are removed and trimmed to circular form as in Figure 3, the edges appearing as at 9. The `undersurface of the button is ground to a convex shape indicated at 10, corresponding to the concave portion 11 of the countersinlr. (It will be understood that the under surface of the button might be concave corresponding to a convex surface of the countersink). The button is so positioned above the countersink concavity 11 that when heated it will drop down without warping and twisting and will be completely fused without bubbles, or other defects, which would impair the value of the resulting lens.

To accomplish this we utilize thin feelers 12 of zinc or other soft metal. Instead of metal feelers there may beemployed feelers formed of suitable metal oxides, or powder mixed with gum or other material adapted to collapse at a predetermined temperature.

We locate the feelers preferably as indicated tain them in proper position with respect to the button and the countersink, We use` a cement. The feelers are touched with Cement as well as the opposite edges of the button, the cement being designated as 13. This serves to cement the feelers to the countersink and buttons so as to hold the several parts in position. While the cement is drying, we employ a spring 14 to holdv the parts in position. lVhen the cement is dry, this spring is removed and the countersink with its button can be easily handled.

The countersink and button, which are not yet fused, may then be placed on a suitable carhorundum slab in the usual way in the metal trough having the bottom 1 and side walls 2 and again inserted in the furnace.

The temperature is then raised to 750 C. approiumately for about 15 minutes approxlmately. Our object is to permit of a progressive fusing of the button from the point where it touches the countersink in the direction of the feelers, so as t'o exclude the air beneath the ,button and between it' and the counter-sink, so that there will be no air bubbles caught between the button and the countersink. l

The temperature is then allowed to fall gradually for annealing purposes. This iS a. very important step in connection with the manufacture of this type of lens which we have found to be especially adaptable to its peculiar requirements.

Where the depression curve 11 is very deep we may use eelers made of harder metal.

We prefer that the inside side Walls 15 of the crown segments or strips 4 to have a partly nished or grey edge l5 as this preyents reflection 'from this edge in the iinal ens.

It will be understood that we desire to comprehend within our invention all the modifications necessary to adapt it to varying conditions and uses.

What we claim is 1. In an apparatus for fusing countersinks, a metallic trough, a strip of inert material on the bottom of the trough such as asbestos, and yielding means adapted to be interposed beinterposed therebetween, and cement applied to said'feelers for engagement with the button and countersink.

4. In combination in the manufacture of a lexis, a countersink, a button, and fusible metal feelers positioned and adapted to hold the button out of contact With'the countersink y tween groups of pieces of glass to be fused into buttons, to force yieldingly said groups outwardly across the side walls of the trough.

2. ln the art of manufacturing fused lenses, a new article of manufacture for car- "rying lenses during fusing, consisting of a trough of metal having side walls, a strip of material on the bottom thereof, upon which the lenses rest and which is not affected by the heat ci the furnace, and yielding means for maintaining the lenses against the side Walls to accommodate the expansion and contraction of the parts while at the same time maintaining the lenses in a predetermined position.

3. In combination in the manufacture oi a lens, a eountersink, a button, soft metal feelers 

